|Year|1905–1911|1912–1915|1915–1918|1918–1921|
|---|---|---|---|---|
|chairperson|T.V. SivaraoPantulu|S. AdinarayanaRao|D. SankaraSastrulu|Shilpa Bendi|
|Year|1921–1926|1926–1929|1929–1931|1931–1938|
|chairperson|ChattiPurnayyaPantulu|M.V. Kamayyashetti|H. Suryanarayana|M.V. Ranganadham|
|Year|1938–1942|1946–1949|1949–1952|1952–1956|
|chairperson|ChallaNarasimhaNaidu|B.V. RamanayyaSetty|GynateVenkatarao|IppiliLaxminarayana|
|Year|1956–1961|1962–1963|1963–1964|1967–1970|
|chairperson|PasagadaSuryanarayana|MaturiRamarao|L. Suryalingam|M.A. Ravuf|
|Year|1970–1972|1981–1992|1995–2000|2000–2005|
|chairperson|IppiliVenkatarao|A.V. Narasimham (varam)|DudaBhavaniSankar|PaidisettiJayanthi|
|Year|2005–present||||
|ChairPerson|M.V. Padmavathi||||

Question: tell me the total number of chairpersons.
Answer: 21